The purpose of this supplemental request is to obtain funds to complete existing studies and extend some of those studies to determine the multiplicity and characteristics of different species of cytochrome P-450 terminal oxidases in liver after induction. The studies include differential induction of the different P-450 species by 3-methyl-cholanthrene (MC) phenobarbital (PB), pregnenolone 16 alpha-carbonitrile (PCN), polychlorinated biphenyls (PCB's), the insecticide DDT, and substrates like the analgesic aminopyrine. Catalytic activities will be determined for a number of substrates, including aminopyrine, ethylmorphine, benzpyrene, biphenyl and testosterone, measuring multiple products and ratios of products formed. Spectral changes on addition of substrates as well as chemicals like methylated xanthines to liver microsomes will be used to learn more about the nature of the type I and reverse type I spectral change. Cytochrome P-450 will be solubilized for comparison of binding spectra of the different induced species with that in microsomes.